Surgical scissors are indispensable tools for surgeons, operating theatre staff and other medical practitioners and are used for cutting and excising patient tissue or sutures. These scissors need to be able to cut cleanly, effectively and accurately, to be robust, and to be suitable for sterilisation. It can be appreciated that accuracy of cutting is important in any surgical procedure. Achieving a clean cut is particularly important for minimising trauma and inflammation to the surrounding tissue.
Conventional surgical scissors comprise two scissor members, each scissor member having a distal blade portion and a proximal handle portion. The blade portion has a cutting edge, a contacting face, an outer face and a distal tip. A finger opening is at the proximal end of the handle portion. The scissor members are pivotally connected to each other at a pivot axis between the blade portion and the handle portion such that their contacting faces can mutually abut when closed. As with conventional scissors, as the distal tips of the blade portions are moved closer together by squeezing together the handle portions, the contacting faces of the blade portions slide relative to each other parallel to their planes. In so doing, the respective cutting edges mutually intersect and contact each other at a point of contact which travels distally along the cutting edges as the blade members come together. Cutting is achieved by the shearing action of the opposed cutting edges of the blade portions at the point of contact. Conventionally, surgical scissors are ergonomically adapted for either left-handed or right-handed use.
This conventional scissor design is ineffective when cutting tough fibrous tissue such as ligaments, or large sections of tissue. In those situations, the blade members of the scissors tend to splay apart or the tissue slips away, thus achieving either an imprecise cut or no cut at all. In addition, the misalignment caused by the blade members splaying apart can result in tissue becoming trapped between the splayed blade members rendering the scissors useless until the trapped tissue is freed. In order to minimise the chances of blade splaying, the surgeon must perform a number of smaller cuts on tough tissue as opposed to one clean cut. However, a series of small cuts, results in an imprecise, untidy and ragged cut; it also prolongs the procedure.
Often, surgical scissors are unable to withstand the rigours of surgery and sterilisation. They may need to be repaired frequently or discarded and replaced. Commonly, the two blades are held against each other by a pivot pin which loosens and increases the risk of the blades splaying apart in use. Also the blades tend to become blunt on recurrent use and hence require frequent sharpening.
A possible way of overcoming some disadvantages of conventional surgical scissors would be to use stiffer blades so that they do not splay apart as readily. Stiffer blades may be achieved by using a stiffer material, which would be more expensive, or by making the blades thicker. However, thicker blades are both undesirable and impractical as the scissors may be too bulky to manoeuvre in confined spaces, heavier and therefore more tiring to use, and more expensive to make. Furthermore, surgeons are familiar with their conventional instruments, particularly with the weight and feel of their instruments in use, therefore it is desirable for any adaptations to conventional surgical scissors to be minimal so that surgeons remain comfortable with using the scissors. In addition, it is desirable for any adaptations to be minimal so as to keep the cost of manufacture low.
JP 2002045582 discloses scissors comprising removable handles. The removable handles are connected together by a guide part so that the handles do not become disassociated from one another when the handles are detached from the blades.
This document does not address the problem of lateral blade splaying in scissors during cutting.
The inventor has previously come up with a solution to the problem of lateral blade splaying. GB 2,423,269 discloses scissors comprising a wedge means on at least one of the handle portions, the wedge means being co-operable with the other handle portion during a cutting stroke to urge the handle portions apart laterally while biasing the blade portions laterally together to oppose relative lateral movement of the blade portions away from each other during the cutting stroke.
There remains a desire for surgical scissors that address the problem of lateral blade splaying, whilst remaining closely related to conventional surgical scissors so as to keep the cost of manufacture low and to increase acceptance in the market.
An object of the present invention is to provide improved scissors that are robust, cut cleanly and effectively and avoid or minimise the disadvantages of current scissors as outlined above.